This article argues that Foucault's 1964 paper “La folie, l'absence d'œuvre” ought to be understood as a response to Derrida's 1963 paper “Cogito et histoire de la folie”. I clarify the chronology of the exchange between these two thinkers and follow commentators Bennington and Flynn in emphasising themes other than the status of madness in Descartes. I undertake a thematic investigation of Foucault's 1961 characterisation of madness as the absence of an œuvre and the role of this characterisation in Derrida's (...) 1963 paper. Then I turn to an investigation of Foucault's substantial change in position on these key themes with his 1964 paper. I argue that Foucault seeks to minimise the initial importance he attributed to his characterisation of madness as the absence of an œuvre, altering his understanding of the relation between madness and language as well as shifting the event that silences madness from Descartes to Freud. Derrida's reconsideration of Foucault's Folie et déraison in 1991 treats Freud as the new locus of the exchange. This is an implicit recognition by Derrida of Foucault's “La folie, l'absence d'œuvre” and confirmation of its place within the exchange. (shrink)